In the current semiconductor industry, integrated circuit products can be divided into three categories: analog circuits, digital circuits, and digital/analog hybrid circuits. Memory device is one important type of the digital circuits. In recent years, flash memory is particularly rapidly developed in memory device filed. A main feature of the flash memory is that the storage information can be maintained for a long term in an unpowered condition. So flash memories are widely used in rewritable data storages that require a variety of data to be stored without a power supply. Further, flash memory has many other advantages, such as high integration, fast access speed, being apt to erase and rewrite, etc. Therefore, flash memories are also widely used in many areas such as micro-electromechanical systems, automated control systems, etc.
With the development of high-density flash memory technology, the performances of various types of portable electronic devices have been improved. Flash memories are commonly used as the memory devices in such portable electronic devices, including digital cameras, laptops, tablet computers, smart phones, etc. Therefore, reducing the size of the flash memory cells and simultaneously reducing the cost of flash memory become one research direction of the technological development.
However, as the size of the flash memory cells reduces, the pitch between adjacent memory cells becomes smaller. Therefore, the adjacent memory cells may be interfered with each other when reading, writing or erasing operations are performed. Such interferences may result in an unreliable performance of the flash memory.